Cornea-mimetic lamellar microstructure and mechanical integrity of bioinspired collagen vitrigel implants

Abstract

Purpose : In recent years, researchers have moved towards biological polymers to create biocompatible corneal substitutes that can potentially integrate well with the surrounding tissue. To this end, we have developed a Type I collagen based vitrigel biomaterials that demonstrate cornea mimetic microstructure, collagen fibril alignment and lamella formation via a controlled self-assembly process using cyclodextrins as modulatory molecules. We evaluated mechanical properties of these materials and lamellar integrity via rheological analysis.

Methods : Implants were prepared using CD and Type 1 collagen solution in appropriate buffer. Samples were subjected to slow vitrification process – slow dehydration at controlled temperature and humidity for 1 week, then rehydrated in PBS. Materials were fixed & processed, and imaged with a Leo FESEM. Hydrated samples were also tested for shear strain resistance using oscillation frequency sweep on a TA Instruments Ares G2 rheometer. Further, materials were subjected to a temperature ramp at constant frequency to determine failure temperature.

Results : The FESEM images (Figure 1) demonstrated cornea mimetic lamellar formation and the alignment of collagen fibers in materials with CD. This effect is also observed in macro-scale, as the lamellae can be carefully separated. Through rheology, storage and loss modulus as a function of frequency of oscillation was obtained. It was determined that the mechanical integrity of the materials can be significantly altered using CD, and were higher than vitrigels without CD (Figure 2).

Conclusions : CD Col membranes demonstrate unique cornea-mimetic properties. Functionalization of cyclodextrins renders it possible to organize and align collagen fibrils, and to control higher order self-assembly processes. This correlates with the observed lamellar structure and fibril alignment observed in addition to the improved structural integrity observed through rheological studies.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

A) Cornea-mimetic implant fabricated with variable thickness and curvatures. B) SEM cross-sectional image on fixated sample show cornea-mimetic lamellae (scale bar = 1 μm). C) SEM angled top view image on shows aligned collagen fibril within lamellae (scale bar = 0.2 μm)

 

Rheological characterization of inherent membrane properties A) Storage modulus of CD-Col vitrigels B) Rheological measurements of Storage and Loss Moduli for αCD Col.